Place a paper towel over the top of the cooker. Close the slow cooker and cook on high-heat setting for 1 hour.

Turn off the slow cooker and open the lid. Remove the crock from the cooker and let cool for about 10 minutes. Run a sharp knife around the edge of cooked cake to loosen, then place the plate on top of the slow cooker and flip it upside down to remove the cake.

Set cooked cinnamon coffee cake aside and let cool. When the cake is completely cooled, sprinkle with powdered sugar and transfer to a cutting board. Cut into wedges and serve with fresh fruit, if desired.